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    <blockquote> <p>I could do this by passing a reference to the MainActivity to the LoginActivity when calling it, and then in the AsyncTask onPostExecute, call a function in that MainActivity instance to refresh the displayed data.</p> </blockquote> <p>The out-of-the-box way of dealing with activities coming and going is to use <a href="https://developer.android.com/reference/android/content/AsyncTaskLoader.html" rel="nofollow"><code>AsyncTaskLoader</code></a>. This approach implements @ByteMe's suggestion to unregister/register activity instances. Unfortunately, its programmer API is... less than painless. In particular, the API is written for a screen that begins loading immediately when it's opened. Using the <a href="https://developer.android.com/guide/components/loaders.html" rel="nofollow">Loaders</a> API in a screen that begins loading upon user interaction is perfectly possible, but the implementation is a bit awkward.</p> <p>A common alternate approach –still using only core- and support-v4 library classes– is to use an <a href="https://developer.android.com/reference/android/app/IntentService.html" rel="nofollow"><code>IntentService</code></a> to do the background work and the <a href="https://developer.android.com/reference/android/support/v4/content/LocalBroadcastManager.html" rel="nofollow"><code>LocalBroadcastManager</code></a> to deliver the result.</p> <p>If using Open Source libraries is an option, you might want to look at <a href="http://square.github.io/otto/" rel="nofollow">Otto Bus</a> or <a href="https://github.com/Netflix/RxJava" rel="nofollow">RxJava</a> to deliver the "load finished" event.</p> <blockquote> <p>Alternatively, in this instance I could just finish() the MainActivity when I start the LoginActivity, and launch a new MainActivity from the onPostExecute which would display the refreshed data.</p> </blockquote> <p>If I understand correctly, the <code>MainActivity</code> is your launch activity. The first thing it does is check if login is necessary and, if it is, it directs to <code>LoginActivity</code>. If login isn't necessary, it shows the account data and if it is, it waits for <code>LoginActivity</code> to return.</p> <p>This sounds to me like a perfect fit for <a href="http://developer.android.com/reference/android/app/Activity.html#startActivityForResult%28android.content.Intent,%20int%29" rel="nofollow"><code>startActivityForResult(Intent, int)</code></a>. Just have the main activity launch the login activity with a request code. The login activity can call <a href="http://developer.android.com/reference/android/app/Activity.html#setResult%28int,%20android.content.Intent%29" rel="nofollow"><code>setResult(int, Intent)</code></a> with a return code and the authentication data. The main activity can then implement <a href="http://developer.android.com/reference/android/app/Activity.html#onActivityResult%28int,%20int,%20android.content.Intent%29" rel="nofollow"><code>onActivityResult()</code></a> to get the return value from the login activity and do all that needs to be done. </p> <p>As an added benefit, you can centralise all <code>SharedPreferences</code> interaction in the main activity and keep it entirely outside login activity. This makes for lower coupling between the two.</p> <p>An entirely different approach that you could consider is to ditch user authentication entirely and rely on <a href="https://developers.google.com/+/" rel="nofollow">Google+ Sign-in</a> to identify users by their Google+ account. You can do the same through <a href="http://developer.android.com/reference/android/app/Activity.html#onActivityResult%28int,%20int,%20android.content.Intent%29" rel="nofollow">Facebook</a>. On the upside, using either of these (or both) will completely free you from the responsibility of managing authentication and credentials in a secure way. On the downside, there's vendor lock-in and it may scare off some users.</p>
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    1. COGreat, startActivityForResult / onActivityResult is exactly what I need, works perfectly. I like the suggestion of passing back the data and centralising the SharedPrefs access, makes more sense. Thanks a million
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